Studies of Phase Transition of Partly Metamict Fergusonite at High Temperature

1 Introduction The mineral whose chemical formula is simply written as YNbOhas naturally two polymorphs: fergusonite and fergusonite-β. The former is tetragonal and the latter is monoclinic. It is difficult to distinguish the original crystallographic features of the mineral because it was metamictized during geological history. This is to say that α-decay events of radioactive elements of uranium and thorium ha the crystal structure of the mineral result in its transferring from crystalline to metamict state. In other words, which crystal